As an approach to characterizing all human ATP-binding cassette (ABC) superfamily genes, a search of the human expressed sequence tag (EST) database was performed using sequences from known ABC genes. A total of 105 clones, containing sequences of potential ABC genes, were identified, representing 21 distinct genes. This brings the total number of characterized human ABC genes from 12 to 33. The new ABC genes were mapped by PCR on somatic cell and radiation hybrid panels and yeast artificial chromosomes (YACs). The genes are located on human chromosomes 1, 2, 3, 4, 6, 7, 10, 12, 13, 14, 16, 17 and X; at locations distinct from previously mapped members of the superfamily. The characterized genes display extensive diversity in sequence and expression pattern and this information was utilized to determine potential structural, functional and evolutionary relationships to previously characterized members of the ABC superfamily.

A total of 100 kb of DNA derived from 69 individual human brain cDNA clones of 0.7-2.0 kb were sequenced by concatenated cDNA sequencing (CCS), whereby multiple individual DNA fragments are sequenced simultaneously in a single shotgun library. The method yielded accurate sequences and a similar efficiency compared with other shotgun libraries constructed from single DNA fragments (> 20 kb). Computer analyses were carried out on 65 cDNA clone sequences and their corresponding end sequences to examine both nucleic acid and amino acid sequence similarities in the databases. Thirty-seven clones revealed no DNA database matches, 12 clones generated exact matches (> or = 98% identity), and 16 clones generated nonexact matches (57%-97% identity) to either known human or other species genes. Of those 28 matched clones, 8 had corresponding end sequences that failed to identify similarities. In a protein similarity search, 27 clone sequences displayed significant matches, whereas only 20 of the end sequences had matches to known protein sequences. Our data indicate that full-length cDNA insert sequences provide significantly more nucleic acid and protein sequence similarity matches than expressed sequence tags (ESTs) for database searching.

>sp|Q9NP58|ABC6_HUMAN ATP-binding cassette, sub-family B, member 6, mitochondrial precursor (Mitochondrial ABC transporter 3) (Mt-ABC transporter 3) (ABC transporter umat) - Homo sapiens (Human).
MVTVGNYCEAEGPVGPAWMQDGLSPCFFFTLVPSTRMALGTLALVLALPCRRRERPAGADSLSWGAGPRISPYVLQLLLA
TLQAALPLAGLAGRVGTARGAPLPSYLLLASVLESLAGACGLWLLVVERSQARQRLAMGIWIKFRHSPGLLLLWTVAFAA
ENLALVSWNSPQWWWARADLGQQVQFSLWVLRYVVSGGLFVLGLWAPGLRPQSYTLQVHEEDQDVERSQVRSAAQQSTWR
DFGRKLRLLSGYLWPRGSPALQLVVLICLGLMGLERALNVLVPIFYRNIVNLLTEKAPWNSLAWTVTSYVFLKFLQGGGT
GSTGFVSNLRTFLWIRVQQFTSRRVELLIFSHLHELSLRWHLGRRTGEVLRIADRGTSSVTGLLSYLVFNVIPTLADIII
GIIYFSMFFNAWFGLIVFLCMSLYLTLTIVVTEWRTKFRRAMNTQENATRARAVDSLLNFETVKYYNAESYEVERYREAI
IKYQGLEWKSSASLVLLNQTQNLVIGLGLLAGSLLCAYFVTEQKLQVGDYVLFGTYIIQLYMPLNWFGTYYRMIQTNFID
MENMFDLLKEETEVKDLPGAGPLRFQKGRIEFENVHFSYADGRETLQDVSFTVMPGQTLALVGPSGAGKSTILRLLFRFY
DISSGCIRIDGQDISQVTQASLRSHIGVVPQDTVLFNDTIADNIRYGRVTAGNDEVEAAAQAAGIHDAIMAFPEGYRTQV
GERGLKLSGGEKQRVAIARTILKAPGIILLDEATSALDTSNERAIQASLAKVCANRTTIVVAHRLSTVVNADQILVIKDG
CIVERGRHEALLSRGGVYADMWQLQQGQEETSEDTKPQTMER